The present invention relates to a display system for traffic information which may be used by vehicle operators to plan or modify an intended route. This information allows a driver of a vehicle to so adjust his itinerary as to avoid heavy congestion caused by accidents, the "letting out" of large gatherings, construction roadblocks and other conditions which modify or disrupt the steady flow of traffic. The congestion problem has long been recognized in many cities of the world; various systems have been conceived to minimize the effects of traffic blockage as it affects an individual driver. These systems have been complex, subject to interference and required the installation of expensive equipment.
A number of systems in the prior art (such as Dahan, U.S. Pat. No. 4,398,171) utilize a television-like screen mounted in the vehicle as a means of displaying traffic information. A map of the city appears on the screen; this map is a repetitive pattern which has been stored in memory elements in the screen circuit. Traffic conditions are monitored by TV cameras mounted above the roads of the city. Signals from the cameras are converted to suitable codes, processed by a computer, and transmitted to a receiver in each vehicle. Suitable symbols are then generated and appear at their proper positions on the map.
In other systems (for example, Madnick et al U.S. Pat. No. 4,792,803 or Pfennighausen et al U.S. Pat. No. 3,283,297) a large number of sensors are buried under roadways or mounted alongside of them. Various parameters such as the number of cars per lane per unit time, the average speed of vehicles along each road, the presence of moisture or fog, etc. are measured and processed in a computer. When conditions are judged to be congestion-producing, various signals are generated and transmitted by radio to those vehicles equipped with the system. This enables the driver in many cases to circumvent the slower traffic.
Perhaps the most popular system in use involves interrupting standard radio broadcasts with bulletins about traffic tie ups on various roads and highways. This information is obtained from helicopters flying above the city, from police accident reports and from incidental observers who report traffic jams to the broadcast station by using car telephones. Although these verbal reports are accurate and obviate the need for complex sensors and computer circuits, the information can often only be used in a limited way by the motorist. He often cannot visualize the area of tie up and therefore cannot plan alternate routes from his position in the traffic pattern.